JP7098564B2 - Imaging lens and imaging device - Google Patents

Description

The present disclosure relates to an image pickup lens and an image pickup apparatus.

Conventionally, as an image pickup lens applicable to an image pickup device such as a digital camera, those described in the following Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4 have been proposed. In Patent Document 1, Patent Document 2, and Patent Document 3, the first lens group having a positive refractive power, the aperture, and the second lens group having a positive refractive power are described in this order from the object side to the image side. An image pickup lens including a third lens group having a refractive power is described. Patent Document 4 describes, in order from the object side to the image side, a first lens group front group having a positive refractive power, an aperture aperture, a first lens group rear group having a positive refractive power, and a negative refractive power. An image pickup lens including a second lens group having the above is described.

Japanese Unexamined Patent Publication No. 2012-0263676 Japanese Unexamined Patent Publication No. 2017-054078 Japanese Unexamined Patent Publication No. 2014-219587 Japanese Unexamined Patent Publication No. 2013-156459

As an image pickup lens applied to the above image pickup device, there is a demand for a lens having a small F-number, high resolution, and a compact size that can ensure good portability of the image pickup device. Patent Document 1 and Patent Document 2 describe lens systems having focal lengths equivalent to 35 mm and 28 mm, respectively, when converted into a 35 mm silver halide film camera. However, the lens systems described in Patent Document 1 and Patent Document 2 have room for improvement in correction of curvature of field and astigmatism in order to achieve the high resolution of the level required in recent years. The lens systems described in Patent Documents 3 and 4 have an F number of 2.8 or more and cannot be said to have a sufficiently small F number, and the overall length of the lens system is long as a lens for a recent digital camera. ..

The present disclosure has been made in view of the above circumstances, and includes an image pickup lens having a small F number, high resolution, high optical performance, and the image pickup lens, although it is compactly configured. It is an object of the present invention to provide an image pickup apparatus.

The image pickup lens according to one aspect of the present disclosure includes a first lens group having a positive refractive force, a aperture, a second lens group having a positive refractive force, and a negative refractive force in this order from the object side to the image side. The first lens group and the second lens group move integrally along the optical axis at the time of focusing, and the third lens group is fixed to the image plane. The first lens group consists of three or less lenses, the lens surface on the most object side of the first lens group is a convex surface, and in the first lens group, the negative lens and the positive lens are sequentially arranged from the object side. The second lens group includes a bonded lens in which at least one negative lens and at least one positive lens are bonded, and a bonded lens. The lens on the most image side of the second lens group including different lenses is a biconvex lens, and the third lens group includes an aspherical lens having a negative refractive force and a negative lens in order from the object side to the image side. The near-axis radius of curvature of the object-side surface of the most image-side biconvex lens of the second lens group is Ra, and the near-axis of the image-side surface of the most image-side biconvex lens of the second lens group. When the radius of curvature is Rb, the following conditional equation (1) is satisfied.
0 <(Ra + Rb) / (Ra-Rb) <1 (1)

It is more preferable that the image pickup lens of the above aspect satisfies the following conditional expression (1-1).
0 <(Ra + Rb) / (Ra-Rb) <0.3 (1-1)

In the image pickup lens of the above aspect, the F number of the image pickup lens is FNo, the distance on the optical axis from the lens surface on the object side to the lens surface on the image side in the state of focusing on an infinite object, and the air of the image pickup lens. When the sum with the back focus at the converted distance is TL and the maximum image height is Ymax, it is preferable to satisfy the following conditional expression (2), and it is more preferable to satisfy the following conditional expression (2-1).
3.5 <FNo × TL / Ymax <7 (2)
4 <FNo × TL / Ymax <6 (2-1)

In the image pickup lens of the above aspect, when the combined focal length of the first lens group and the second lens group is fG12 and the focal length of the image pickup lens in the state of being in focus on an infinity object is f, the following conditional equation (3) Is preferable, and it is more preferable to satisfy the following conditional expression (3-1).
0.6 <fG12 / f <0.9 (3)
0.6 <fG12 / f <0.85 (3-1)

In the image pickup lens of the above aspect, when the focal length of the image pickup lens in a state of being in focus on an infinite object is f and the maximum image height is Ymax, it is preferable that the following conditional expression (4) is satisfied, and the following conditional expression (4) is satisfied. It is more preferable to satisfy 4-1).
1 <f / Ymax <1.8 (4)
1.45 <f / Ymax <1.7 (4-1)

In the image pickup lens of the above aspect, it is preferable that the lens surface on the most object side of the second lens group is a concave surface.

In the image pickup lens of the above aspect, the second lens group is composed of a negative lens having a concave surface facing the object side, a positive lens having a convex surface facing the image side, and an aspherical lens in order from the object side to the image side. It may be configured as.

In the image pickup lens of the above aspect, the radius of curvature of the near axis of the surface of the second lens from the image side of the second lens group on the image side is Rc, and the near surface of the biconvex lens on the image side of the second lens group is close to the object side. When the axis of curvature radius is Ra, it is preferable to satisfy the following conditional expression (5), and it is more preferable to satisfy the following conditional expression (5-1).
-0.5 <(Rc + Ra) / (Rc-Ra) <0.5 (5)
-0.45 <(Rc + Ra) / (Rc-Ra) <0.45 (5-1)

In the image pickup lens of the above aspect, when the refractive index of the biconvex lens on the most image side of the second lens group with respect to the d line is Nd23, it is preferable that the following conditional expression (6) is satisfied, and the following conditional expression (6-1) is satisfied. ) Is more preferable.
1.75 <Nd23 (6)
1.8 <Nd23 <2.2 (6-1)

The image pickup apparatus according to another aspect of the present disclosure includes an image pickup lens according to the above aspect of the present disclosure.

In addition, "consisting of" and "consisting of" in the present specification refer to lenses having substantially no refractive power other than the listed components, and lenses such as an aperture, a filter, and a cover glass. It is intended that optical elements other than the above, as well as mechanical parts such as a lens flange, a lens barrel, an image pickup element, and an image stabilization mechanism, and the like may be included.

In addition, the "group having a positive refractive power" in the present specification means that the group as a whole has a positive refractive power. Similarly, "having a negative refractive power-group" means having a negative refractive power as a whole group. "Lens with positive refractive power" and "positive lens" are synonymous. "Lens with negative refractive power" and "negative lens" are synonymous. The "-lens group" is not limited to a configuration consisting of a plurality of lenses, but may be a configuration consisting of only one lens. "Single lens" means a single lens that is not joined.

A compound aspherical lens (a lens in which a spherical lens and an aspherical film formed on the spherical lens are integrally formed and function as one aspherical lens as a whole) is regarded as a junction lens. Instead, treat it as a single lens. Unless otherwise specified, the sign of refractive power, surface shape, and radius of curvature of a lens including an aspherical surface will be considered in the paraxial region. Regarding the sign of the radius of curvature, the sign of the radius of curvature of the surface having the convex surface facing the object side is positive, and the sign of the radius of curvature of the surface having the convex surface facing the image side is negative.

The "back focus at the air conversion distance" used in the conditional expression is the air conversion distance on the optical axis from the lens surface on the image side to the focal position on the image side. The "focal length" used in the conditional expression is the paraxial focal length. Unless otherwise specified, the values used in the conditional expression are values when the d line is used as a reference in a state where the object is in focus at infinity. The "d-line", "C-line", and "g-line" described herein are emission lines, with a d-line wavelength of 587.56 nm (nanometers) and a C-line wavelength of 656.27 nm (nanometers). ), The wavelength of the g-line is 435.84 nm (nanometers).

According to the present disclosure, it is possible to provide an image pickup lens having a small F-number, high resolution, high optical performance, and an image pickup device provided with the image pickup lens, although the size is small. ..

It is sectional drawing which corresponds to the image pickup lens of Example 1 of this disclosure, and shows the structure and the luminous flux of the image pickup lens which concerns on one Embodiment of this disclosure. It is sectional drawing which shows the structure of the image pickup lens of Example 1 of this disclosure. It is sectional drawing which shows the structure of the image pickup lens of Example 2 of this disclosure. It is sectional drawing which shows the structure of the image pickup lens of Example 3 of this disclosure. It is sectional drawing which shows the structure of the image pickup lens of Example 4 of this disclosure. It is sectional drawing which shows the structure of the image pickup lens of Example 5 of this disclosure. It is each aberration diagram of the image pickup lens of Example 1 of this disclosure. It is each aberration diagram of the image pickup lens of Example 2 of this disclosure. It is each aberration diagram of the image pickup lens of Example 3 of this disclosure. It is each aberration diagram of the image pickup lens of Example 4 of this disclosure. It is each aberration diagram of the image pickup lens of Example 5 of this disclosure. It is a perspective view of the front side of the image pickup apparatus which concerns on one Embodiment of this disclosure. It is a perspective view of the back side of the image pickup apparatus which concerns on one Embodiment of this disclosure.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing the configuration of an image pickup lens according to an embodiment of the present disclosure. The example shown in FIG. 1 corresponds to the image pickup lens of the first embodiment described later. In FIG. 1, the left side is the object side and the right side is the image side, showing a state in which the object is in focus at infinity. Further, FIG. 1 also shows an axial luminous flux 2 and a luminous flux 3 having a maximum angle of view as the luminous flux.

Note that FIG. 1 shows an example in which a parallel plate-shaped optical member PP is arranged on the image side of the image pickup lens on the assumption that the image pickup lens is applied to the image pickup device. The optical member PP is a member that assumes various filters and / or a cover glass and the like. The various filters are, for example, a low-pass filter, an infrared cut filter, a filter that cuts a specific wavelength range, and the like. The optical member PP is a member having no refractive power, and a configuration in which the optical member PP is omitted is also possible.

The image pickup lenses of the present disclosure include a first lens group G1 having a positive refractive power, an aperture aperture St, and a second lens group G2 having a positive refractive power in order from the object side to the image side along the optical axis Z. And a third lens group G3 having a negative refractive power. The aperture stop St shown in FIG. 1 does not show the shape but shows the position on the optical axis.

This image pickup lens has an advantage in shortening the overall length of the lens system by adopting a telephoto type configuration in which positive, positive, and negative lens groups are arranged in order from the object side to the image side. Since the Petzval sum generated in the positive first lens group G1 and the positive second lens group G2 can be reduced by the Petzval sum generated in the negative third lens group G3, the Petzval sum of the entire image pickup lens can be suppressed. This is advantageous in suppressing curvature of field. By arranging the aperture stop St between the first lens group G1 and the second lens group G2, the off-axis luminous flux is transferred to the image plane Sim of the main light beam as compared with the case where the aperture stop stop St is arranged on the image side of this position. Since the incident angle can be reduced, it is not necessary to take a long back focus in order to reduce the incident angle, and as a result, it is advantageous to shorten the total length of the lens system.

In the image pickup lens of the present disclosure, the first lens group G1 and the second lens group G2 move integrally along the optical axis Z at the time of focusing, and the third lens group G3 with respect to the image plane Sim. It is fixed. In addition, "moving integrally" means moving in the same direction and by the same amount at the same time. Compared with the configuration in which the entire image pickup lens is moved during focusing, the image pickup lens of the present disclosure can reduce the burden on the drive mechanism for focusing, which is advantageous for miniaturization of the apparatus. The parentheses and double arrows below the first lens group G1 and the second lens group G2 shown in FIG. 1 are focus groups in which the first lens group G1 and the second lens group G2 move integrally when they are in focus. It means that there is.

As an example, in the image pickup lens shown in FIG. 1, the first lens group G1 is composed of two lenses L11 to L12 in order from the object side to the image side, and the second lens group G2 is from the object side to the image side. The third lens group G3 is composed of three lenses L21 to L23 in order, and the third lens group G3 is composed of three lenses L31 to L33 in order from the object side to the image side. However, the number of lenses constituting the first lens group G1 and the second lens group G2 may be different from the number shown in FIG. 1.

However, the first lens group G1 is configured to consist of three or less lenses. By reducing the number of lenses constituting the first lens group G1 to 3 or less, it is advantageous for miniaturization. The lens surface on the most object side of the first lens group G1 is a convex surface, and this configuration also favors miniaturization. The first lens group G1 includes a bonded lens in which a negative lens and a positive lens are joined in order from the object side and the joint surface has a convex surface facing the object side. By joining the negative lens and the positive lens, it is advantageous for correction of chromatic aberration and miniaturization. Further, by joining the negative lens and the positive lens in order from the object side and forming the joint surface so that the convex surface faces the object side, it is advantageous to suppress the occurrence of the difference in spherical aberration due to the wavelength. In addition, it is advantageous for correcting astigmatism and chromatic aberration of magnification, and is also advantageous for widening the angle.

The second lens group G2 is configured to include a bonded lens in which at least one negative lens and at least one positive lens are bonded, and a lens different from the bonded lens. The inclusion of at least one set of junction lenses in the second lens group G2 is advantageous for correcting chromatic aberration. Further, the inclusion of a lens different from the junction lens in the second lens group G2 is advantageous for aberration correction. When the second lens group G2 includes an aspherical lens as a lens different from the junction lens, it is advantageous for correcting curvature of field and astigmatism. Further, the lens on the most image side of the second lens group G2 is configured to be a biconvex lens having a biconvex shape. This configuration is advantageous in suppressing the occurrence of spherical aberration.

The lens surface on the most object side of the second lens group G2 is preferably a concave surface. In this case, it is possible to prevent the off-axis light rays from being greatly refracted by the concave surface and the convex surface of the image side surface of the biconvex lens on the image side of the second lens group G2, whereby the amount of aberration generation can be prevented. Can be suppressed.

As an example, the second lens group G2 consists of three lenses, a negative lens having a concave surface facing the object side, a positive lens having a convex surface facing the image side, and an aspherical lens in order from the object side to the image side. Can be configured from. In the second lens group G2, arranging the negative lens and the positive lens in order from the object side is advantageous for correcting chromatic aberration. By making the surface of the negative lens on the object side of the second lens group G2 concave on the object side and the surface on the image side of the positive lens continuously arranged on the image side of the negative lens as a convex surface, the off-axis light beam Can be avoided from being greatly refracted, whereby the amount of aberration generated can be suppressed. Placing the aspherical lens on the most image side of the second lens group G2 is advantageous for correcting astigmatism. Further, by limiting the number of lenses constituting the second lens group G2 to three, it is advantageous to shorten the total length of the lens system.

The third lens group G3 is configured to include an aspherical lens having a negative refractive power, a negative lens, and a positive lens in this order from the object side to the image side. The aspherical lens of the third lens group G3 is advantageous for correcting astigmatism. Since the negative lenses arranged continuously on the image side of the aspherical lens can reduce the Petzval sum generated in the positive first lens group G1 and the positive second lens group G2, the petzval sum of the entire image pickup lens can be reduced. The Petzval sum can be suppressed, which is advantageous for correcting the curvature of field. Placing a positive lens on the most image side of the third lens group G3 is advantageous for correcting distortion.

Next, the configuration related to the conditional expression will be described. In the image pickup lens of the present disclosure, the near-axis radius of curvature of the surface of the biconvex lens on the most image side of the second lens group G2 on the object side is Ra, and the surface of the biconvex lens on the image side of the second lens group G2 on the image side. When the paraxial radius of curvature is Rb, the following conditional equation (1) is satisfied. The occurrence of astigmatism can be suppressed by making sure that the value does not fall below the lower limit of the conditional expression (1). By not exceeding the upper limit of the conditional expression (1), it is possible to prevent the refractive power of the surface on the image side of the biconvex lens on the image side of the second lens group G2 from becoming too strong, and spherical aberration can be prevented. It can be suppressed. If the configuration satisfies the following conditional expression (1-1), better characteristics can be obtained.
0 <(Ra + Rb) / (Ra-Rb) <1 (1)
0 <(Ra + Rb) / (Ra-Rb) <0.3 (1-1)

F number of the image pickup lens is FNo, the distance on the optical axis from the lens surface on the most object side of the image pickup lens to the lens surface on the image side of the image pickup lens in the state of focusing on an infinity object, and the air of the image pickup lens. When the sum with the back focus at the converted distance is TL (hereinafter, TL is referred to as the total length of the lens system) and the maximum image height is Ymax, it is preferable to satisfy the following conditional expression (2). The FNo used in the conditional expression (2) is an open F number. By making sure that the value does not fall below the lower limit of the conditional expression (2), the F number does not become too small with respect to the image height, so that aberrations such as spherical aberration can be easily corrected. By not exceeding the upper limit of the conditional expression (2), the total length of the lens system does not become too long with respect to the image height, which is advantageous for miniaturization or for realizing an optical system with a small F number. It becomes. If the configuration satisfies the following conditional expression (2-1), better characteristics can be obtained.
3.5 <FNo × TL / Ymax <7 (2)
4 <FNo × TL / Ymax <6 (2-1)

When the combined focal length of the first lens group G1 and the second lens group G2 is fG12 and the focal length of the image pickup lens in the state of being in focus on an infinite object is f, the following conditional expression (3) can be satisfied. preferable. By making sure that the value does not fall below the lower limit of the conditional expression (3), it is advantageous to reduce the aberration fluctuation during focusing. By not exceeding the upper limit of the conditional expression (3), it becomes easy to shorten the movement amount of the focus group at the time of focusing, which is advantageous for miniaturization. If the configuration satisfies the following conditional expression (3-1), better characteristics can be obtained.
0.6 <fG12 / f <0.9 (3)
0.6 <fG12 / f <0.85 (3-1)

When the focal length of the image pickup lens is f and the maximum image height is Ymax in a state of being in focus on an infinite object, it is preferable to satisfy the following conditional expression (4). By preventing the focal length from becoming less than the lower limit of the conditional expression (4), the focal length does not become too short, so that the wide-angle lens does not become excessively widened, which is advantageous for correcting curvature of field. By not exceeding the upper limit of the conditional expression (4), the focal length does not become too long, which is advantageous in shortening the total length of the lens system. If the configuration satisfies the following conditional expression (4-1), better characteristics can be obtained.
1 <f / Ymax <1.8 (4)
1.45 <f / Ymax <1.7 (4-1)

The near-axis radius of curvature of the image-side surface of the second lens from the image side of the second lens group G2 is Rc, and the near-axis radius of curvature of the object-side surface of the most image-side biconvex lens of the second lens group G2 is Ra. If so, it is preferable to satisfy the following conditional expression (5). By making sure that the value does not fall below the lower limit of the conditional expression (5), the occurrence of spherical aberration can be suppressed. By preventing the condition from exceeding the upper limit of the conditional expression (5), the occurrence of astigmatism can be suppressed. If the configuration satisfies the following conditional expression (5-1), better characteristics can be obtained.
-0.5 <(Rc + Ra) / (Rc-Ra) <0.5 (5)
-0.45 <(Rc + Ra) / (Rc-Ra) <0.45 (5-1)

When the refractive index of the biconvex lens on the most image side of the second lens group G2 with respect to the d line is Nd23, it is preferable to satisfy the following conditional expression (6). By making the condition not less than the lower limit of the conditional expression (6), it is advantageous to shorten the total length and to suppress the spherical aberration from being insufficiently corrected. Further, it is preferable to satisfy the following conditional expression (6-1). By not not being less than the lower limit of the conditional expression (6-1), it is advantageous to shorten the total length, and it is advantageous to suppress the spherical aberration from being insufficiently corrected. By preventing the spherical aberration from exceeding the upper limit of the conditional expression (6-1), it is advantageous to suppress excessive correction of spherical aberration.
1.75 <Nd23 (6)
1.8 <Nd23 <2.2 (6-1)

The above-mentioned preferable configuration and possible configuration including the configuration related to the conditional expression can be any combination, and it is preferable that they are appropriately and selectively adopted according to the required specifications. According to the present disclosure, it is possible to realize an image pickup lens having a small F number, high resolution, and high optical performance, even though it is compactly configured. In addition, "the F number is small" here means that the F number is 2.5 or less.

Next, an example of the image pickup lens of the present disclosure will be described.
[Example 1]
FIG. 2 shows a cross-sectional view showing the configuration of the image pickup lens of the first embodiment. FIG. 2 differs from FIG. 1 in that the luminous flux is not shown, but since the basic drawing method and configuration are as described above, some duplication will be omitted here. The image pickup lens of Example 1 has, in order from the object side to the image side, a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and negative refraction. It is composed of a third lens group G3 having power. When focusing from an infinite object to the nearest object, the first lens group G1 and the second lens group G2 move integrally along the optical axis Z, and the third lens group G3 becomes an image plane Sim. On the other hand, it is fixed. The first lens group G1 is composed of two lenses L11 to L12 in order from the object side to the image side, and the second lens group G2 consists of three lenses L21 to L23 in order from the object side to the image side. It is composed of lenses, and the third lens group G3 is composed of three lenses L31 to L33 in order from the object side to the image side. The lens L11 and the lens L12 are joined to each other. The lens L21 and the lens L22 are joined to each other. The lens L22 and the lens L23 are arranged with an air gap in between. The lens L23 and the lens L31 are aspherical lenses. The above is the outline of the image pickup lens of Example 1.

For the image pickup lens of Example 1, the basic lens data is shown in Table 1, the specifications are shown in Table 2, and the aspherical coefficient is shown in Table 3. In Table 1, the Sn column shows the surface number when the surface on the object side is the first surface and the number is increased by one toward the image side, and the R column shows the radius of curvature of each surface. In the column D, the surface distance between each surface and the surface adjacent to the image side on the optical axis is shown. Further, the column of Nd shows the refractive index of each component with respect to the d-line, and the column of νd shows the Abbe number of each component with respect to the d-line.

In Table 1, the sign of the radius of curvature of the surface having the convex surface facing the object side is positive, and the sign of the radius of curvature of the surface having the convex surface facing the image side is negative. Table 1 also shows the aperture stop St and the optical member PP. In Table 1, the surface number and the phrase (St) are described in the column of the surface number of the surface corresponding to the aperture stop St. The value in the bottom column of D in Table 1 is the distance between the surface on the image side and the image surface Sim in the table.

Table 2 shows the focal length f of the image pickup lens, the back focus Bf in terms of air equivalent distance, and the F number FNo. , The maximum total angle of view 2ω, the total length TL of the lens system, and the maximum image height Ymax are shown with reference to the d-line. (°) in the column of 2ω means that the unit is degrees. The values shown in Table 2 are values when the d line is used as a reference in a state where the object is in focus at infinity. The F number FNo. shown in Table 2 and the aberration diagram described later. Corresponds to the F number FNo used in the conditional expression (2).

In Table 1, the surface numbers of the aspherical surface are marked with *, and the numerical value of the radius of curvature of the near axis is described in the column of the radius of curvature of the aspherical surface. In Table 3, the surface number of the aspherical surface is shown in the Sn column, and the numerical value of the aspherical surface coefficient for each aspherical surface is shown in the columns of KA and Am. It should be noted that m is an integer of 3 or more and differs depending on the surface. For example, in the aspherical surface of the first embodiment, m = 3, 4, 5, ..., 20. “E ± n” (n: integer) of the numerical value of the aspherical coefficient in Table 3 means “× 10 ^{± n} ”. KA and Am are aspherical coefficients in the aspherical expression expressed by the following equation.
Zd = C × h ² / {1 + (1-KA × C ² × h ² ) ^1/2 } + ΣAm × h ^m
however,
Zd: Aspherical depth (the length of a perpendicular line drawn from a point on the aspherical surface at height h to a plane perpendicular to the optical axis in which the aspherical apex is in contact).
h: Height (distance from the optical axis to the lens surface)
C: The reciprocal of the radius of curvature of the near axis KA, Am: the aspherical coefficient, and the aspherical Σ means the sum with respect to m.

In the data in each table, degrees are used as the unit of angle and mm (millimeter) is used as the unit of length. Units can also be used. In addition, in each table shown below, numerical values rounded to a predetermined digit are listed.

FIG. 7 shows each aberration diagram of the image pickup lens of Example 1. In FIG. 7, spherical aberration, astigmatism, distortion, and chromatic aberration of magnification are shown in order from the left. In the spherical aberration diagram, the aberrations on the d-line, C-line, and g-line are shown by solid lines, long dashed lines, and alternate long and short dash lines, respectively. In the astigmatism diagram, the aberration on the d-line in the sagittal direction is shown by a solid line, and the aberration on the d-line in the tangential direction is shown by a short dashed line. In the distortion diagram, the aberration on the d line is shown by a solid line. In the chromatic aberration of magnification diagram, the aberrations in the C line and the g line are shown by long dashed lines and alternate long and short dash lines, respectively. FNo. Of the spherical aberration diagram. Means F number, and ω in other aberration diagrams means a half angle of view.

Unless otherwise specified, the symbols, meanings, description methods, and illustration methods of the respective data relating to the above-mentioned Example 1 are the same in the following Examples, and thus duplicate description will be omitted below.

[Example 2]
FIG. 3 shows a cross-sectional view showing the configuration of the image pickup lens of the second embodiment. The image pickup lens of Example 2 has the same configuration as the outline of the image pickup lens of Example 1. For the image pickup lens of Example 2, the basic lens data is shown in Table 4, the specifications are shown in Table 5, the aspherical coefficient is shown in Table 6, and each aberration diagram is shown in FIG.

[Example 3]
FIG. 4 shows a cross-sectional view showing the configuration of the image pickup lens of the third embodiment. The image pickup lens of Example 3 has the same configuration as the outline of the image pickup lens of Example 1. For the image pickup lens of Example 3, the basic lens data is shown in Table 7, the specifications are shown in Table 8, the aspherical coefficient is shown in Table 9, and each aberration diagram is shown in FIG.

[Example 4]
FIG. 5 shows a cross-sectional view showing the configuration of the image pickup lens of the fourth embodiment. The image pickup lens of Example 4 has the same configuration as the outline of the image pickup lens of Example 1. For the image pickup lens of Example 4, the basic lens data is shown in Table 10, the specifications are shown in Table 11, the aspherical coefficient is shown in Table 12, and each aberration diagram is shown in FIG.

[Example 5]
FIG. 6 shows a cross-sectional view showing the configuration of the image pickup lens of Example 5. In the image pickup lens of the fifth embodiment, the first lens group G1 is composed of three lenses L11 to L13 in order from the object side to the image side, the lens L11 is a single lens, and the lens L12 and the lens L13. It has the same configuration as the outline of the image pickup lens of the first embodiment except that the lenses are joined to each other. For the image pickup lens of Example 5, the basic lens data is shown in Table 13, the specifications are shown in Table 14, the aspherical coefficient is shown in Table 15, and each aberration diagram is shown in FIG.

Table 16 shows the corresponding values of the conditional expressions (1) to (6) of the image pickup lenses of Examples 1 to 5. In Examples 1 to 5, the d line is used as a reference wavelength. Table 16 shows the values on the d-line basis.

As can be seen from the above data, the image pickup lenses of Examples 1 to 5 have an F number of 2.2 or less, a small F number, and various aberrations are satisfactorily corrected, although they are compactly configured. It is possible to achieve high resolution and realize high optical performance.

Next, the image pickup apparatus according to the embodiment of the present disclosure will be described. 12 and 13 show external views of the camera 30, which is an image pickup apparatus according to an embodiment of the present disclosure. FIG. 12 shows a perspective view of the camera 30 as viewed from the front side, and FIG. 13 shows a perspective view of the camera 30 as viewed from the rear side. The camera 30 is a so-called mirrorless type digital camera, and the interchangeable lens 20 can be detachably attached. The interchangeable lens 20 includes an image pickup lens 1 according to an embodiment of the present disclosure, which is housed in a lens barrel.

The camera 30 includes a camera body 31, and a shutter button 32 and a power button 33 are provided on the upper surface of the camera body 31. Further, on the back surface of the camera body 31, an operation unit 34, an operation unit 35, and a display unit 36 are provided. The display unit 36 displays the captured image and the image within the angle of view before being captured.

A shooting opening for incident light from a shooting target is provided in the central portion of the front surface of the camera body 31, a mount 37 is provided at a position corresponding to the shooting opening, and the interchangeable lens 20 is connected to the camera body 31 via the mount 37. It is attached to.

In the camera body 31, an image pickup device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Sensor) that outputs an image pickup signal corresponding to a subject image formed by the interchangeable lens 20 and an image pickup element thereof are output. A signal processing circuit that processes an image pickup signal to generate an image, a recording medium for recording the generated image, and the like are provided. With this camera 30, it is possible to shoot a still image or a moving image by pressing the shutter button 32, and the image data obtained by this shooting is recorded on the recording medium.

Although the techniques of the present disclosure have been described above with reference to embodiments and examples, the techniques of the present disclosure are not limited to the above embodiments and examples, and various modifications are possible. For example, the radius of curvature, the interplanar spacing, the refractive index, the Abbe number, the aspherical coefficient, and the like of each lens are not limited to the values shown in the above embodiments, and may take other values.

Further, the image pickup apparatus according to the embodiment of the present disclosure is not limited to the above example, and may have various aspects such as a camera other than the mirrorless type, a film camera, a video camera, and the like.

1 Imaging lens 2 On-axis optics 3 Maximum angle of optics 20 Interchangeable lens 30 Camera 31 Camera body 32 Shutter button 33 Power button 34, 35 Operation unit 36 Display unit 37 Mount G1 1st lens group G2 2nd lens group G3 3rd Lens group L11 to L13, L21 to L23, L31 to L33 Lens PP Optical member Sim Image plane St Aperture aperture Z Optical axis

Claims (15)

From the object side to the image side, it consists of a first lens group having a positive refractive power, an aperture, a second lens group having a positive refractive power, and a third lens group having a negative refractive power.
At the time of focusing, the first lens group and the second lens group move integrally along the optical axis, and the third lens group is fixed to the image plane.
The first lens group consists of three or less lenses.
The lens surface on the most object side of the first lens group is a convex surface.
The first lens group includes a bonded lens in which a negative lens and a positive lens are joined in order from the object side and the joint surface has a convex surface facing the object side.
The second lens group includes a bonded lens in which at least one negative lens and at least one positive lens are bonded, and a lens different from the bonded lens.
The lens on the most image side of the second lens group is a biconvex lens.
The third lens group consists of an aspherical lens having a negative refractive power, a negative lens, and a positive lens in order from the object side to the image side.
When the near-axis radius of curvature of the object-side surface of the biconvex lens of the second lens group is Ra, and the near-axis radius of curvature of the image-side surface of the biconvex lens of the second lens group is Rb.
0 <(Ra + Rb) / (Ra-Rb) <1 (1)
An image pickup lens that satisfies the conditional expression (1) represented by. The F number of the image pickup lens is FNo,
TL is the sum of the distance on the optical axis from the lens surface on the object side to the lens surface on the image side in the state of being in focus on an infinite object, and the back focus at the air-equivalent distance of the image pickup lens.
When the maximum image height is Ymax,
3.5 <FNo × TL / Ymax <7 (2)
The image pickup lens according to claim 1, which satisfies the conditional expression (2) represented by. The combined focal length between the first lens group and the second lens group is fG12,
When the focal length of the image pickup lens in the state of being in focus on an infinite object is f,
0.6 <fG12 / f <0.9 (3)
The imaging lens according to claim 1 or 2, which satisfies the conditional expression (3) represented by. The focal length of the image pickup lens in the state of being in focus on an infinite object is set to f.
When the maximum image height is Ymax,
1 <f / Ymax <1.8 (4)
The image pickup lens according to any one of claims 1 to 3, which satisfies the conditional expression (4) represented by. The imaging lens according to any one of claims 1 to 4, wherein the lens surface on the most object side of the second lens group is a concave surface. The second lens group is any of claims 1 to 5, which comprises a negative lens having a concave surface facing the object side, a positive lens having a convex surface facing the image side, and an aspherical lens in order from the object side to the image side. The image pickup lens according to item 1. When the paraxial radius of curvature of the surface of the second lens from the image side of the second lens group on the image side is Rc,
-0.5 <(Rc + Ra) / (Rc-Ra) <0.5 (5)
The image pickup lens according to any one of claims 1 to 6, which satisfies the conditional expression (5) represented by. When the refractive index of the biconvex lens of the second lens group with respect to the d line is Nd23,
1.75 <Nd23 (6)
The imaging lens according to any one of claims 1 to 7, which satisfies the conditional expression (6) represented by. 0 <(Ra + Rb) / (Ra-Rb) <0.3 (1-1)
The imaging lens according to claim 1, which satisfies the conditional expression (1-1) represented by. 4 <FNo × TL / Ymax <6 (2-1)
The image pickup lens according to claim 2, which satisfies the conditional expression (2-1) represented by. 0.6 <fG12 / f <0.85 (3-1)
The imaging lens according to claim 3, which satisfies the conditional expression (3-1) represented by. 1.45 <f / Ymax <1.7 (4-1)
The imaging lens according to claim 4, which satisfies the conditional expression (4-1) represented by. -0.45 <(Rc + Ra) / (Rc-Ra) <0.45 (5-1)
The imaging lens according to claim 7, which satisfies the conditional expression (5-1) represented by. 1.8 <Nd23 <2.2 (6-1)
The imaging lens according to claim 8, which satisfies the conditional expression (6-1) represented by. An image pickup apparatus comprising the image pickup lens according to any one of claims 1 to 14.

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